Understanding the LyncDiscover Service

The LyncDiscover service was introduced in Lync Server 2010 to provide autodiscovery of Lync services to Lync mobile clients. In Lync Server 2013, this service will also provide autodiscovery of services to the Lync 2013 desktop and tablet clients. The LyncDiscover service can be compared to the Exchange Server Autodiscover Service. The simple principle is that users will connect to a web address, authenticate, and then request the next server to connect to for appropriate services. In Lync Server 2013, the LyncDiscover service will provide web URLs for mobility as well as SIP servers for clients such as Front End and Edge Servers. This enables organizations to simplify the deployment of Lync clients of all types.

The LyncDiscover service runs as a web service on all Lync Front End and Director Servers. When mobility is enabled in a 2010 environment, or on all 2013 environments, the LyncDiscover IIS directory will be created. The goal of the LyncDiscover service is to provide Lync clients with a valid home server to register against. Requests to LyncDiscover are authenticated before delivering service information using WebTicket authentication. When a sign-in request is started by a client, the client will end the requesting user’s SIP URI in the request. When the LyncDiscover receives the HTTPS request from the client and validates the WebTicket provided by the client, it will identify the home server of the requesting user and then deliver critical information for client registration to the client. This will include the following:

• Web service URL to connect to Mobility Services

• Front End Server FQDN for SIP client connectivity

• FQDN and port of the Access Edge Service associated with the Front End Server pool for remote SIP client connectivity

The LyncDiscover service operates on a static DNS entry. All clients will try to connect to LyncDiscover.<sipdomain> and LyncDiscoverinternal.<sipdomain>. For a user in the companyabc.com SIP domain, this FQDN would be LyncDiscover.companyabc.com. Whereas the Lync 2013 desktop client will fail back to DNS SRV record lookup for discovery, the mobile and tablet clients, including Windows 8, will only look for LyncDiscover. This service is absolutely critical for any Lync deployments for client sign-in.

The “Putting It All together: Protocol Flow” section provides details on the messages exchanged between the client and the server for LyncDiscover.